This invention relates to implantable assemblies comprising treatment material reservoirs for providing a treatment material, such as a drug in fluid form, directly to the vascular system of a mammal. A number of such assemblies are known, and may be broadly described as having a housing which defines a reservoir for holding the treatment material, and a catheter leading from the housing for interconnecting the reservoir with the vascular system. Existing implantable assemblies are adapted to be sutured into place within the body.
The existing assemblies known to the inventor are of two types. The first type has a catheter permanently affixed to the reservoir housing. Such permanent affixation makes the assembly awkward to implant. The second type has a catheter which fits over a male tube projecting from the housing, and is secured thereto by placing an external collar about the catheter. This assembly permits the housing to be sutured in position, and the catheter to be installed in a vein and sized before connection of the catheter to the housing. However, the connection of the catheter requires care and it relies solely on elastic gripping to remain attached. It is desirable to provide an implantable reservoir device which permits the direct and simple yet secure connection to a catheter after the suturing of the reservoir housing in the body and the placement and sizing of the catheter. EP-A 0119596 has the catheter secured in position by an annular protrusion on the male tube rather than by a collar.
The present invention is an implantable assembly as defined in claim 1. Preferred features of the assembly are recited in the sub-claims following claim 1.
Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figures 1 and 2 show a cutaway pictorial view of an implantable assembly according to the present invention. Device 1 of the assembly includes a body portion or housing 2 defining a generally cup-shaped recess, chamber or cavity forming a reservoir 5 for holding treatment fluids or medicine. Housing 2 has an open face which is closed off by a septum or cover 3 held down by a retaining ring 4. Cover 3 is formed of a self-resealing polymer, which is preferably an elastomer such as a silicone rubber or latex, and is adapted to permit access using a hypodermic needle to the reservoir 5 formed by the cover 3 and the housing 2. Housing 2 is formed of a biocompatible material, such as electropolished 316L stainless steel, or other surgical grade steel or biocompatible hard material. At the base of the reservoir 5 a protection plate 6 formed of a suitable material, such as a high durometer silicone rubber, is placed to prevent damage to a needle tip. Housing 2 has a generally cup-shaped form, rising from a base plate 7. Plate 7 has apertures 8 therein evenly spaced about the perimeter of the housing for suturing the device 1 to a layer of tissue when implanting. Also shown in Figure 1 is a syringe 9 having a non-coring needle 10. Syringe 9 is shown by way of illustration having penetrated the septum or cover 3, in position to refill the reservoir. A catheter 11 leads from the reservoir to the vascular system of the subject.
Figure 2 shows a schematic section of the device 1 implanted beneath the skin of a mammal. As shown, device 1 lies beneath the skin 12 in the sub-cutaneous tissue 13 of the mammal. One or more sutures 14 through apertures 8 of the base plate 7 attach device 1 to the muscle fascia 15, and catheter 11 leads from the housing to the vascular system 16 of the mammal. The housing 2 of device 1 has a low profile and a broad flat base. This geometry orients the septum 3 to face outwardly toward the skin, so that the reservoir may be repeatedly and conveniently refilled. Needle 10 is shown in position to refill the reservoir.
It will be appreciated that because device 1 is sutured directly to the mammal, a high degree of manoeuverability of the device or accessibility of the suture apertures 8 is desired for the surgical process of implantation. However, because device 1 connects directly via catheter 11 to the vascular system, the integrity of the catheter connection must also be assured. Furthermore, it is desirable to size the length of the catheter after one end has been placed into a vein and the catheter threaded into position. According to the present invention these ends are achieved by providing in the housing a low profile locking means 20 adapted to receive a separate twist-lockable catheter connector 17 which fits over the sized catheter. Safety means secures the twist-locked catheter to the housing in fixed orientation.
Figures 3A, 3B show views of a catheter end twist-lock connector. Figures 4A, 4B and 4C show corresponding mating locking portion 20 on the housing 2 of device 1, adapted to receive the catheter connector 17 shown in Figures 3A, 3B in accordance with the invention.
Figure 3A is a perspective view from the catheter end of flanged catheter connector 17. Connector 17 comprises a peripheral flange 18 and a central portion or tubular body 19 having a bore 30 therethrough for fitting over a catheter in such a manner as to be slidably moved therealong. Flange 18 comprises opposed arcuate flange segments 18A, 18B extending radially outward from central portion 19. Flange 18 has a cross-dimension d1 in a first direction and a cross-dimension d2 in a second direction angularly offset therefrom. Connector 17 also includes a tab 27, discussed further below in relation to Figure 5.
Figure 3B shows a section through the connector of Figure 3A. As shown, flange segments 18A, 18B extend in a direction radially outward from the central flow axis of the catheter. Inwardly thereof, central portion defines a generally tubular body 19 oriented along the catheter flow axis. The tubular body 19 serves as a collar, and has an inner diameter calculated to elastically compress the catheter when the catheter has been slipped over a cannula to attach it to the reservoir.
Figure 4A shows a bottom view of housing 2 of the device 1 for receiving a catheter 11 and connector 17. As shown, the housing comprises the substantially disc-shaped base plate 7 having apertures 8 evenly spaced about the perimeter thereof. A vertical T slot serving as locking portion 20 is formed in base plate 7 with the axis "A" of the T oriented along a radius of the disc. Slot 20 comprises an axial portion serving as input region 21 and an interior region or cross portion 22. As shown, axial portion 21 is aligned with a radius of the base plate 7 and cross portion 22 is perpendicular thereto. The width D1 of axial portion 21 is slightly greater than the width d1 in the narrow direction of flange 18 of the catheter connector 17 (Figure 3A) to which it is matched, and less than d2. Thus the catheter connector 17 may be slidably fitted into the T slot along axis A. Cross portion 22 has a width greater than axial portion 21, allowing rotation of the connector. Thus, when the catheter connector 17 is moved axially into axial portion 21 and butted up against the housing 2, rotation of the catheter connector 17 within cross portion 22 results in positioning the flange 18 behind an inner or confronting surface 24 of cross portion 22. Surface 24 thus traps the catheter connector 17 within the T-slot 20 in the manner of a bayonet mount to prevent axial motion thereof. Figure 4A also shows cannula 31, which is press fit into the housing 2 so as to provide a fluid outlet from the reservoir. Cannula 31 in a prototype embodiment is a straight tube, having a diameter small enough so that the catheter may be slidably fitted thereover, yet large enough to firmly compress the catheter when the catheter connector 17 is placed over the catheter.
Figure 4B shows a side view along the central axis A of the T slot 20 and housing 2. Housing 2 has an outlet aperture or exit port 26 formed along the axis A of slot 20, and communicating directly to the reservoir 5. Cannula 31 is fitted by an interference fit in aperture 26 for receiving the catheter prior to sliding the catheter connector 17 along the T-slot. A rotation of the catheter connector 17 then engages its flange segment 18A, 18B behind an extending arm of which a surface (24 of Figure 4A) thereby engages the catheter connector firmly to prevent its pulling away from the housing. This establishes secure fluid communication between the reservoir and the catheter.
Figure 4C shows a vertical section along the outflow axis "A" of the device 1. A face 32 of housing 2 lying perpendicular to axis A is preferably milled flat when forming the T-slot. The cup-shaped central recess or chamber of the housing is a stepped bore, which defines the reservoir 5 and a circular recess for holding the elastomeric cover or septum (not shown). The cannula 31 extends from the reservoir to receive a catheter.
Figure 5 shows a top view of device 1 with the twist-lock catheter connector 17 mounted in position. As shown, the catheter connector has been inserted in the T-slot and rotated so as to bring flange 18 into engagement behind inner surface 24 of the cross portion of the T. In this position, tab 27 protruding from connector 17 is brought down flush against the base plate 7. Tab 27 is shown held by a structure which provides positive resistance to counter-rotation of the catheter connector 17 which might lead to its detachment. The tab 27 lies in a plane oriented, with respect to the flange 18 of the connector 17 so as to assure that, when held in position against base plate 7, flange 18 is held fully rotated in slot 20, whereby the connector is positively locked in the housing. In the preferred embodiment tab 27 has an aperture 28 therethrough, and may be sutured down against the base plate 7 with sutures 29. The sutures 29 pass through corresponding holes in the base plate 7, shown as holes 8a in Figure 4A. Catheter 11 is compressed between the inner face of the central portion or tubular body 19 of the connector, and the cannula 31 (Figures 4A-4C). In addition, when the connector 17 is installed, the catheter "bunches up" at 11a into a thickened donut-shaped mass which provides an axially directed elastic force along axis A. The resultant pressure between flange 18 and surface 24 further inhibits rotation of connector 17.
Figure 6 shows a perspective view of an implantable assembly having two reservoirs, with the numbered elements corresponding to the identically numbered parts of Figures 1 to 5.
Figure 6A shows a detail of a preferred embodiment of a multi-reservoir implantable assembly, such as the assembly of Figure 6, but having formed thereon bumps or other tactile features which may be felt through the skin when implanted, to identify a reservoir thereof. Retaining ring 4 has a scalloped upper surface with such bumps 34 thereon, so that the bumps 34 outline the cover or septum 3 in a manner easily felt from outside the body. Thus the bumps indicate the location of a reservoir or injection site. In the event it is desired to have more than two reservoirs, which may be placed in a cloverleaf or other cluster configuration, the tactile features preferably include different arrangements of tactile features which additionally each serve as a "code" for the particular medicine which is to be held by that reservoir.
Furthermore the tactile features for distinguishing may take various forms, from a single bump to a coded pattern, and may be placed upon the cover septum itself, or other palpable portion of the body portion.